The present invention relates generally to devices for regulating the flow of intravenous fluids. More specifically, it relates to devices that permit the selection of any of a plurality of discrete flow rates for the continuous infusion of intravenous liquids.
In the medical field, therapeutic or medicinal liquids are often administered to a patient by intravenous (IV) infusion system. In an infusion system, the liquid is typically contained in a reservoir (a bag or a bottle) suspended above the patient, and delivered through a tube, by the force of gravity, to an IV needle inserted into the patient=s vasculature. Alternatively, the liquid may be delivered from a reservoir by an infusion pump.
It is sometimes necessary to control the flow rate at which the liquid is delivered to the patient, particularly when the liquid is to be administered continuously over an extended period of time. The flow rate may be varied depending on, for example, the specific medical treatment, type of medicinal or therapeutic agent, or the specific needs of a particular patient. Indeed, a specific patient's need or demand for a particular drug or other agent may vary over time.
A variety of devices and techniques have been devised to control the flow rate of an IV-administered agent. For example, a clamp may be provided on the IV tubing to restrict the flow rate through the tubing. The technique does not, however, permit precise metering or control of the flow rate. Another device that purports to control the flow rate through an IV system is disclosed in U.S. Pat. No. 5,318,515—Wilk. In this device, a housing contains a plurality of flow control tubes of different cross-sectional areas that are connected to an inlet that receives the liquid from the reservoir through an inlet tube. A selector mechanism on the housing allows the flow path through one or more of the flow control tubes to be selectively opened to a housing outlet, which is connected by an outlet tube to the IV needle. By opening different combinations of the flow control tubes, any of a plurality of discrete flow rates can be selected. While this approach has shown promise, improvements have been sought that would provide more precise selection and control of fluid flow rates, in a device that is inexpensive to manufacture, and simple and reliable to use.
Thus, there has been a need for a device that allows the selection of any of a plurality of discrete flow rates in an IV system, and that also combines a relatively high degree of precision in the selected flow rate with ease of changing the selected flow rate. There has been a further need for a device in which the selected flow rate remains stable over time. In addition, such a device should be easy and inexpensive to manufacture, so that it may be economically made as a disposable item, while providing a high degree of reliability in use.